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Thank you, very interesting.
Where I am here near Cambridge and the observatory in La Palma were both rated Bortle 4 in 2015. However the former is near the top of the scale and has a sky brightness of 20.58 mag / arcsec^2 and the latter 21.58. I suspect the difference may be more marked now. Certainly the sky looks much darker in LP and the Milky Way is spectacular on a clear night at new moon. M31 is obvious from there but difficult from here in the UK. So many stars are visible that I have difficulty recognizing constellations!
The app and firmware updated nicely this evening.
I have also downloaded seestar_alp (https://github.com/smart-underworld/seestar_alp) which works remarkably well and is much more controllable than the Seestar app. It can send the S50 to a specified position in RA/Dec (either Jnow or J2000 epochs), those data can be typed in, pasted from the clipboard or transferred from Stellarium. It also has a scheduler for fully unattended usage. Very highly recommended and I hope that the official ZWO app takes some of the features on board. The app has finally caught up with seestar_alp in that it now does mosaic mode.
Of course, just as I was getting the hang of seestar_alp this evening the sky clouded over completely and I didn’t get a single image.
Thanks. It looks like a generic problem as your image also shows rings around the brighter stars.
Not a deal breaker as photometry is very tolerant of slightly blurred and/or trailed images and I want to do science and not artwork.
Anyway, such artefacts can often be cleaned up in post-processing.
It appears that my image is not properly focused. It should be obvious, but wasn’t, that auto-focus should be run every time before taking images. One day I will print a Bahtinov mask to see how well AF works. Reports are that it is pretty good.
Thanks. It looks like a generic problem as your image also shows rings around the brighter stars.
Not a deal breaker as photometry is very tolerant of slightly blurred and/or trailed images and I want to do science and not artwork.
Anyway, such artefacts can often be cleaned up in post-processing.
Now that I seem to have control over most of the needed functionality, I turn to image quality.
Only one object has been imaged so far, Albireo or β Cyg. It was taken on a poor night but during the only clear spell so far available. Bear in mind that thin haze may have been present. The image shown is the green channel of the 40s stacked image. β Cyg B shows a very obvious ring around it, measured at a radius of 14 arcsec from the center of the stellar image. Other fainter stars show similar rings at 11-14 arcseconds radius. The radius Airy disk of a 50mm aperture in green light is 2.4 arcsec (and pretty much the same for FWHM) and the first bright diffraction ring should be at 5.4 arcsec assuming I calculated correctly. Much less than 14 arcsec anyway. The image scale is 2.37 arcsec/pix according to astronomy.net; this is a good match to the Airy disk size.
Any ideas what may be causing this? Stray reflections is one possibility that comes to mind, as is rather bad spherical aberration.
I will take more images on properly clear nights to see whether the effect is reproducible but I would be interested to learn whether other Seestar users experience the same effects. If not, perhaps it should be fixed / or exchanged under warranty.
Here’s the image which shows the ring.
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Thanks Diane. Turns out that I had already done that without noticing. Once station mode was started properly a file browser on the Linux box could also see the internal storage and was able to copy the individual frames.
Also: wrt Bluetooth I found that giving the app permission to chane system setting was necessary. Not at all sure that is wise from a security point of view so may disable it again and rely on station mode for access within range of the wifi and USB cable when I am on the road.
Thanks Steve.
I found that connecting the USB cable to a Windows PC makes the FITS files available as an external storage device. It doesn’t (yet) work on a Linux box.
Initial experiments with station mode were not very productive but as I don’t really know what I am doing, perhaps that may be expected.
TFM is woefully inadequate and saving individual frames is presently beyond my ability. That will almost certainly change fairly soon.
Paul
OK, so far, so good. A brief gap in the clouds allowed an image of Albireo to be taken. Only four images were successful, it seems, out of an imaging session which lasted two or three minutes, but lets let that go for a moment.
The only way I could find to get them off the phone was to connect a USB cable and use the file browser to copy them to the local disk. Again, lets let that go for a moment.
There were 5 files, corresponding to four 10-second subs and a stack of four. All the files are in JPEG format and the stack is included here.
Next question: I would like to do precision photometry, so how can raw FITS files be created by the Seestar app in a place which is generally accessible? The JPEG shows clear artifacts which I would prefer not to have imposed. AIUI, the raw images can be saved and transferred.
Thanks,
PaulAttachments:
Thanks both.
I have a series of questions but will deal with them one at a time to help reduce confusion. Further, please note that I know very little about this system, in part because of the woefully limited documentation that ZWO provides, so may have some completely false assumptions and preconceptions.
First concerns set-up. I thought that the S50 would use Bluetooth to communicate with an Android phone. At initialization time the S50 states “Need bluetooth access to search Seestar nearby” and it is necessary to set the phone’s Wifi connection to the 10.0.0.0/8 local network created by the S50. Connection then proceeds satisfactorily but, of course, the phone no longer has access to the internet — seriously crippling other important features.
I have tried everything I can think of to configure the phone to allow the use of Bluetooth, without success. The phone will happily pair with other devices, such as a laptop so much is clearly working.
Any suggestions? If it helps, the Seestar firmware is V2.95
Torrential rain this evening for me on La Palma
Torrential rain and high winds for me that evening brought down the box of electronics on the microwave dish providing internet connectivity. Last night a friend discovered it lying in a puddle of water. Verimax have already fixed things, which is excellent service by a ISP, given that they only learned about the issue less than 6 hours ago.
Relevance to comets? Kevin Hills is an avid observer and his robotic observatory is on my site, sharing the internet link with me.
Now fixed. Impressive service from Verimax — under 4 hours from notification to a working connection.
Looks like I got out just in time! I flew back to the UK on Thursday.
To be fair, La Palma badly needs some rain.
I am very seriously considering buying a Seestar S50.
Very impressive results have come out over the last year. Not only “pretty pictures” but also hard science. As far as I can tell, they can do precision photometry (my principal interest) down to at least 13th magnitude.
The only thing holding me back is a rumour that at 80mm version may be released Real Soon Now.
When on holiday a GP I know tells people they’re a vet.
Two things:
1) a friend of mine fell off his bicycle outside a vet’s practice. He was given excellent first aid.
2) Vets need to know at least something about almost everything medical concerning warm-blooded animals. They are generalists par excellence. To be honest, I would rather be treated for relatively minor injuries by a vet than by a brain surgeon or gynaecologist.I’m working on it, at least in part through SGL. I recently pointed out the contrast with Cambridge University, where the 160 year old Thorrowgood and 191 year old Northumberland telescopes are still in frequent use.
In the end I suspect that the Golden Rule will apply. They who have the gold make the rules. I would certainly contribute some of my (virtual) gold to a restoration effort but I doubt that I could fund it all myself. Anyone here willing to step up as treasurer of a charitable trust?
Paul
